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Get a Grip!

In this experiment, you will measure your gripping power. You will see if your gripping power changes as you grip an object for a longer time. You will also compare your gripping power with your classmates.

Programming Language

Subjects

Grades

Objective & Learning Goals

Use a computer and a Gas Pressure Sensor to measure your gripping power.

Write a computer program to measure gripping power.

See which of your hands has the greater gripping power.

Learn what happens to your gripping power as time goes by.

Compare your gripping power with your classmates.

Materials

computer with Birdbrain Robot Server and Scratch

plastic bottle

Hummingbird board

Vernier BTA Sensor Adapter for Hummingbird

1-hole stopper with tapered valve

Vernier Gas Pressure Sensor

heavy-wall plastic tubing

Procedure

Connect the plastic bottle to the pressure sensor as shown below.

Connect the Vernier BTA sensor adapter to the Hummingbird. Then connect the pressure sensor to the adapter. The jumper on the adapter should be set to 0-5 V.

To read a measurement from the pressure sensor, you will use the HB voltage block in Scratch. This block will read a voltage between 0 and 5 V.

The Vernier manual for the pressure sensor provides a linear equation that you can use to convert voltage to pressure: pressure = 51.71*voltage – 25.86

In this experiment, you will grip the bottle as hard as you can for 60 s. You want to record data during this time and compare the data from 0 -10 s with the data from 50 – 60 s. To do this, you will need to write a program that meets the following requirements:

The program must record 480 pressure sensor measurements and store them in a list.

The program should wait 0.125 seconds between measurements (so the program takes approximately 8 measurements per second).

The program must use the function above to calculate the pressure based on the HB voltage block.

The program should graph the pressure measurements to the screen. The pressure measurements should be scaled so that this graph occupies most of the screen. The stage backdrop should show appropriate axes for this graph.

The program should calculate the mean pressure for the entire 60 s period and display this value for the user.

The program should calculate the mean pressure during the period 0 – 10 s and display this value for the user.

The program should calculate the mean pressure during the period 50 – 60 s and display this value for the user.

Grip the bottle as hard as you can with one hand while you run your program. Remember not to start the program until you are gripping as hard as you can. Record your data in the table below.

Repeat this process for your other hand. Record your data in the table.

Data

Processing the Data

In the space provided in the data table, subtract to find the difference between your 0–10 s average and your 50–60 s average for each hand.

Record the 0–60 s results for the other students in your group. Calculate and record your group average. Calculate and record the class average for 0–60 s.

Which of your hands is stronger? Explain your decision.

Did your gripping power increase or decrease during the 60 s period? Why did it change?

How does your grip compare with the class average?

What did you learn about your strength in this experiment? Were you surprised?

Extension

Can you motivate yourself (or someone else) to grip harder? Use lights, motors, and/or sounds to make a robot that does different things depending on how hard the person is gripping. For example, maybe more LEDs light up the harder the person grips. Does the average grip pressure increase when someone uses your device?